Everything said above. Recent research points out that doing slow controlled breathing, where you inhale for 4 counts, exhale for 6, and then take a couple of regular breaths before starting the next cycle works best. This is because the longer exhale gets rid of the carbon dioxide, which is what causes a lot of anxiety symptoms. You can even see changes in people's brains if you do an F MRI. When they are doing this kind of breathing. I start my clients off doing 30 seconds of this breathing, ten times a day. This way, it's both preventative, in that it brings HR and BP down and keeps your neurotransmitters like cortisol down, as well as interventional, i.e., you can use it in the moment. Also quick muscle tension and release from the head down works, too